Practical issues in nuclear resonant vibrational spectroscopy for measuring biological samples: special problems, solutions and some perspectives

Nuclear resonant vibrational spectroscopy (NRVS) is a synchrotron based modern vibrational spectroscopy starting in mid 1990s. This review article focuses on a series of practical issues presented in NRVS for measuring biological samples, which have dilute concentrations, complicated molecular structures and unstable/meta stable enzymatic/chemical states. The main sections (Sec. 2 to Sec. 6) discuss the special problems facing these circumstances and the solutions to the problems. The example tasks include obtaining extra incident beam flux, calibrating energies for sectional scans, reducing real sample temperatures, reducing background counts while keep NRVS signal levels, manipulating and monitoring samples, as well as judging the best simulations. All these are critical for successful measurement and understanding of a bio-NRVS spectrum, especially of the one with extremely weak feature(s), e.g. the iron-hydride(s) inside various hydrogenases. The last section (Sec. 7) provides the readers with information about the latest researches and enlightenments about the future researches. In addition, Sec. 1 provides a simple but still explanatory introduction for NRVS beginners. This article will especially be useful as an overall guide for NRVS users, beamline scientists, and biochemists who make biological samples to work together on the entangled multiple discipline problems facing bio-NRVS. It will also provide general enlightenment for other spectroscopists to resolve entangled issues in their measurements and researches, especially in vibrational spectroscopies and synchrotron related spectroscopies.